Abstract
Moving objects help generate expectations about accompanying sounds and can facilitate early auditory processing of stimuli that match these expectations. At times, a moving object may become occluded by an obstruction; it is unclear to what extent such disruptions to the visual input affect the expectations about subsequent sounds associated with the visual object. We conducted two experiments that examined how dynamic visual input, either fully visible or occluded, influences visual expectations of an ensuing sound. EEG was recorded from adults who passively viewed a red ball that appeared either on the far left or right edge of the display and continuously traversed along the horizontal midline to make contact and bounce off the opposite edge, eliciting a sound at the point of collision. Experiment 1 (n=19) consisted of three conditions: 1) sound with full visual input: a ball was visible when colliding and making a bouncing sound; 2) sound with some visual input: a ball was occluded halfway and not visible during the bouncing sound; 3) sound with no visual input. Experiment 2 (n=17) systematically varied the amount of occlusion to better understand how much visual information is necessary to elicit expectations (AV-full, AV-2/3 – least occluded, AV-1/2, AV-1/3 – most occluded). Our analyses focused on a late slow-wave event-related potential (ERP) measured at occipital electrode sites prior to the onset of the sounds, and revealed differences in the amplitude across the occlusion conditions. In particular, the experiments show that visual occlusion elicits greater slow-wave negativity compared to non-occluded visual input. Overall, these results suggest that occlusion of a dynamic object results in the deployment of neural resources devoted to generating expectations about the timing of an impending auditory event.